Condensation of isobutyraldehyde with lower aliphatic aldehydes



United States Patent- CONDENSATION OF ISOBUTYRALDEHYDE WITH LOWER ALIPHATIC ALDEHYDES Hugh J. Hagemeyer, Jr., Longview, Tex., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application June 28, 1954, Serial No. 439,865

7 Claims. c1. 260 -602) This invention is concerned with an improved process for the production of mixed aldols of isobutyraldehyde. It is concerned with a process wherein isobutyraldehyde and lower aliphatic aldehydes are reacted in the form of mixed aldols by carrying out the condensation in the presence of an alkali metal carbonate. It is specifically concerned with a process for the production of hydroxypivalaldehyde by reacting isobutyraldehyde and formaldehyde at temperatures from 50-90 C. in the presence of an alkali metal carbonate. The invention is further concerned with a process wherein the lower aliphatic aldehyde is added to a reaction vessel containing an excess of isobutyraldehyde and the alkali metal carbonate and heated to a temperature of 50-90 C. It is further concerned with a process for producing mixed aldols of isobutyraldehyde which avoids the formation of other aldol products, and of the usual Cannizzaro and Tischenko reaction products. It is also specifically concerned with a process for the production of hydroxypivalaldehyde wherein formaldehyde is reacted with at least a molar excess of isobutyraldehyde in the presence of an alkali metal carbonate at a temperature in the range of 50-90" C. Then substantially pure hydroxypivalaldehyde is obtained by separating the organic layer and stripping off unchanged isobutyraldehyde.

No prior art process has been reported in which the mixed aldol of isobutyraldehyde and a, lower aliphatic aldehyde is substantially the sole product. Hydroxypivalaldehyde has been prepared from isobutyraldehyde and formaldehyde in the presence of potassium carbonate by Wesseley, Monatshefte 21, 216-234 (1900). Later experiments using this same procedure are reported by Fourneau et al., Bull. Soc. Chim. (4), 47, 871 (1930) and Stiller et al., J. Am. Chem. Soc., 62, 1785 (1940). In the prior art references, relatively large amounts of potassium carbonate were added to equimolar parts of isobutyraldehyde and formalin at low temperatures, -20 C. Some of the disadvantages of this prior art method werelow yields, long reaction times, large catalyst requirements, and incomplete reaction of the formaldehyde. I have found that mixed aldols of isobutyraldehyde may be prepared, by a process in which a relatively small amount of alkali metal carbonate is used, a fast reaction time is obtained and complete reaction of the formaldehyde or other aldehyde used with isobutyraldehyde, is realized. In addition the formation of condensation products other than the mixed aldol is avoided by carry-' ing out the reaction at or above the reflux temperature of isobutyraldehyde. It is an object of my invention to provide such a process. 7

The process of the present invention makes use of the discovery that isobutyraldol is completely dealdolized at about 60 C. I'have found that mixed aldols of isobutyraldehyde with formaldehyde and aldehydes containing from 2-10 carbon atoms do not dealdol ize at ice temperatures in the range of 50-90 C. Thus, I have found it possible to carry out a mixed aldol condensation of isobutyraldehyde with another aldehyde in a temperature range such that no isobutyraldol is formed. If the reaction is carried out according to the process of the invention, and the aldehyde to be condensed with isobutyraldehyde is added to a solution of hot isobutyraldehyde containing the alkali metal carbonate catalyst, the sole product of the reaction is a 3-hydroxy-2,2-dimethy1 aldehyde.

ISO-C. (CHshCHCHO RCHO 15-0-8 RCH(OH)C(C .1):CHO

wherein R is hydrogen or a 1-9 carbon alkyl radical.

In producing the mixed aldol products, and particularly in preparing hydroxypivalaldehyde, it is advantageous to use at least a one mole excess of isobutyraldehyde so that a complete recovery of the hydroxypivalaldehyde is realized in the organic layer. In the process of the present invention I have found that optimum results are obtained by employing molar excesses of iso butyraldehyde ranging from 1 to 5. The catalyst is usually a solution of potassium, sodium or lithium carbonate in water and the weight of catalyst used varies with the particular aldehydes reacted. Thus, in making hydroxypivalaldehyde and employing a one mole excess of isobutyraldehyde, I have found it advantageous to use 4% potassium carbonate based on the weight of isobutyraldehyde charged to the reactor.

Mixed aldols of isobutyraldehyde with formaldehyde,

acetaldehyde, propionaldehyde and butyraldehyde arev made according to the invention by adding the aldehydes to a refluxing solution of isobutyraldehyde in the presence of aqueous potassium carbonate. Although any soluble" alkali carbonate may be used, potassium carbonate is usually preferred and the amount used can vary from 210% based on the weight of isobutyraldehyde charged to the reactor. The catalyst is preferably charged as.a 20-50% aqueous solution in water. Reaction temperatures varying from 50-90 C. have been used and I have found that the optimum results are usually obtained in the temperature range 60-75 C. At temperatures below this broader range, aldol products other than the mixed aldol are formed and at temperatures above 90 C., there is considerable yield loss due to the formation of the Tischenko product of the mixed aldol. This is avoided in the present process by adding the aldehyde to be reacted to isobutyraldehyde at reflux in the presence of aqueous potassium carbonate, and after the addition is complete the organic layer is separated from the aqueous catalyst solution, the excess isobutyraldehyde is stripped off and the product is then distilled at reduced pressure.

This method avoids yield loss due to other condensation reactions since the mixed aldol is heat stable in the absence of the catalyst solution.

Table I contains comparative results obtained using the method described in the prior art and the process of the present invention in preparing hydroxypivalaldehyde from isobutyraldehyde and formaldehyde. In addition to the higher conversions and yields obtained by the process of the present invention, it is immediately obvious that there is no loss of reagents to the formation of higher condensation products and the aldehyde being added to the isobutyraldehyde is substantially completely reacted."

This is particularly advantageous where hydroxypivalaldehyde is being made, since it avoids any of the difficulties involved in destroying or removing residual traces of formaldehyde. I

aeineea TABLE I Mole Ratio, Catalyst, Weight Reaction Reaction i-HBu, HOPA, Run No l-HBu/ Solvent Percent Temp., Time Percent Percent CHzO C. Conv. Yield.

,-l:1 'DHsOHM. .0.5.KOH. 20-25 47 28 1:1 CHsOHHI '0.5"K0H 20-25 83 80 .2:J11.H20c 43562003- 160470 91 90 .2:1. H20 160 .70 86 97 2:1 "H50" 60 70 82- 91 $231 1120.. '60-70 93 04 2:1 E10 60-62 No reaction 2:1 Hi 0 10 112 73 2:1 H2O... .10 109 79 2:1. H2 KzC 60-100 96 70 1. 1:1 H20 4:0 K2003 "SW89 '84 74 'In Table I, the isobutyraldehyde percent conversion represents the amount ofisobutyraldehyde reacted under the conditions employed. RunsNos. 1, 2,134, .and137 show the results using alcoholic and aqueous alkali at lower temperatures. Here the isobutyraldehyde reacted was considerably more than the fhydroxypivalalde'hyde yield due to the formation of other products. In .12un22 the reaction temperature was allowed to go to 100 and in -this run a considerable amount of the hydroxypivalalde-- hyde was converted to the .glycol -.ester by the Tischenko reaction. In run 23 only a tenth mole excess of isobutyraldehyde was employed and again a yield loss was experienced due to a cross Cannizzaro reaction between hydroxypivalaldehycle and formaldehyde to form the pentaglycol.

Table II summarizes the results obtained in the preparation of the mixed aldols of isobutyraldehyde with acetaldehyde, propionaldehyde and normal butyi'aldehyde. Although comparative data on operations outside of the invention is not given, the advantages of this method of preparing mixed aldols of isobutyraldehyde over that wherein an alkali metal hydroxide is used at low temperature should be immediately obvious to those skilled in the art. Thus, the only product obtained is the mixed aldol of isobutyraldehyde and the added aldehyde, and no isobutyraldol or aldol of the added aldehyde is formed.

TABLE II N0. of 1 Niixed Added Moles. K 00 Reaction Reaction i-HBu, ldol, Aldehyde Excess Weight Temp. Time, I Cone. Yield i-HBu Percent 0. hours Percent Percent 1 4:0 "60-75 2 91 90 2 2. 0 60-70 l 2 88 L96 .2. 0 00-62 2 .97 97 1 4:0 60'70 4 '93 91 1 4. 0 60-70 4 92 96 1 4. 0 60-70 3 Q0 92 2 3. 0 60-70 4 06 '97 The invention is further illustrated by the following Eleven hundred fifty grams of isobutyraldehyde and 56 grams of potassium carbonatewdissolved'in 90 grams of water were-added .to a stirred three-necked flask and heated to reflux. Six hundred fifty .grams of a 37% formalin solution was added over a period of 30 minutes and the reaction temperature was held below 70 C. by cooling as necessary. The reaction mixture was stirred at 65- 70 -C. for twohours and at the end of this time the mixture was allowed to cool to 40 C. and the organic layer decanted. Unchanged isobutyraldehyde was distilled off and the residue was distilled at reduced .pressure. Seven hundred ninety grams of hydroxypivalaldehyde, boiling point 7885 C. at 4 mm. was obtained. The hydroxypivalaldehyde dimerized on standing andformed a white crystalline dimer, meltingpoint 92- 94 C This reaction runs very well on a continuous-basis by passing the reaction products through a condenser and 1 then to a decanting step. The isobutyraldehyde" which is distilled off thereafter is returned to the reaction continuously, the reaction being operated at 62-64 C hyde was added to 1,150 grams of .isobutyraldehyde at reflux in the presence of 46 grams of potassium carbonate dissolved'in90 grams of water over a one-hour period. The reaction temperature was maintained at 60-70 C and at the end of the addition the mixture was heated an additional two hours at 70 C. 'The reaction mixture was cooled to 40 C. and the organic layer decanted. Excess isobutyraldehyde was distilled oif at atmospheric pressure and the residue was distilled through a JO-plate column at reduced pressure to yield 1,061 grams of 3- hydroxy-2,2-dimethylhexaldehyde, boiling point 125 C at 14 mm.

Example 3 Example 4 Using the same procedure as in Example 2, 8 moles of propionaldehyde were reacted with -a-mo1ar excess of isohutyraldehyde and a 96% yield of 3-hydroxy-2,2-dimethylvaleraldehyde, boiling point 98 C. at 2-0 mm. was obtained.

Sodium carbonate can also be used in the above ex-- amples.

I claim:

1. A process for the preparation of hydroxypivalaldehyde wherein saidaldehyde is produced in extremely high yield and is substantially the sole aldolproduct, which comprises adding formalin to excess isobutyraldehyde maintained at 50-90 -C. in contact with aqueous potassium carbonate.

2. A processfor the preparation of an aldol product of the formula RCH(OH) C(CHa zCHO isobutyraldehyde solution .being maintained at 50 to I C. during the reaction.

3. A ,process according to claim .2 wherein the iso butyraldehyde is present in a 1-5 mole excess, the alkali metal carbonate being aqueous. potassium carbonate.

4. A process according to claim 2 wherein the added aldehyde is formaldehyde.

5. A process according to claim 2 wherein the added OTHER REFERENCES aldehyde is acetaldehyde. 1

6. A process according to claim 2 wherein the added g fg Monat fur Chemie, vol pages 4 aldehyde is pmpionaldehyde Kohn' Monat fur Chemie vol 22 a es 23 and 24. A PIIOCGSS according to claim 2 wherein the added 5 Lieben: Monat. fur Chemie, vol. 22, pges 291-98. aldehyde 1S n'butymldehyde' Wessely: Monat. fur Chemie, v01. 21, pp. 216-220 1900 Refe'ences cted m the file Patent Stiller et al.: J. Am. Chem. Soc. 62, p. 1787 1940 UNITED STATES PATENTS 2,468,710 Hull' Apr. 26, 1949 2,684,385 Biribouer et a1. July 20, 1954 

2. A PROCESS FOR THE PREPARATION OF AN ALDOL PRODUCT OF THE FORMULA 